Warning: A nasty data-loss bug when copying between external drives

I have to conclude that if you like your data, you can't trust it to HFS+ and the Finder.

Using 10.5.1., I decided to try to consolidate some backups by moving files from one external drive to a second external drive. The operation would ultimately require movement of about 250GB of data.

I thought copying using Finder was safe. I was wrong.

Put simply, some of the files have other ownership, so when I dragged them to the new disk, I am warned that I might have to enter my administrator's password. Fair enough. But I was never prompted. The operation simply failed.

None of the files were copied to the new disk. But they were DELETED from the old disk. Remember, this is a copying operation between two devices, not a move.

They are just gone. Not so much as a see-ya, later dude, or tootle-pip.


This is data that the US taxpayer has funded collecting via federal research grants. Some of it may not be replaceable.

I came across reports of this bug, but it was claimed to have been fixed in 10.5.1. It obviously was not.

I've since discovered that this bug is biting a lot of people:



I've since found that using tar to archive a directory on one disk by writing to the other seems to work. I haven't yet thoroughly tested cp -r to determine whether this bug is in the Finder or lower-level. I want to back everything else up first before I experiment further.


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I am not trying in any way to minimize the importance of this bug, but things like "This is data that the US taxpayer has funded collecting via federal research grants." have a way to irritate me :)

I suppose that the same taxpayer is also paying the salary of the person handling the data, and of the person responsible for making backups of it (which might or might not be the same), and I would think that fact more annoying than the bug itself. Maybe I have long stopped believing there can be any excuse for poor backup strategies.

But it might just be me, of course :)

Much easier to blame the victim, eh?

Well, I hope in your far superior backup strategy that you should never happen upon such a problem. I was consolidating data so I could devote a 700 GB drive to Time Machine, FWIW.

Sorry I irritated you by pointing out that the data might be more important than your garbage, fanboy.

What a rude response

Sorry I irritated you by pointing out that the data might be more important than your garbage, fanboy.

What a rude response. Any sympathy I had for your loss was destroyed by that comment.

FX's irritation is valid, by the way. If your data was as important as you say, you should have had a better backup strategy in place. I too have data funded with federal grants, and knowing how important that data is, I keep regular backups off-site. Any Finder bug, no matter how serious, would not have affected me. I think you've done a disservice to the taxpayers who funded your research.

Important Data

Regardless of who paid for what data, I value all of it. I also value regular backups, either to my external drives and off-site. But I believe the point of the Finder being buggy stands. I mean, if I am copying some recently downloaded PDF files to my external drive and the Finder just wipe them out, I'll be angry too. I wouldn't have use Retrospect or any other software just to copy those files. The Finder should be enough.

I haven't face this particular bug myself, and I regularly move several Mbs of data to and from USB, FW400 and FW800 external drives. Any particularity you can point out about the operation you performed, wgscott?

On the subject of backups

If confirmed, this is certainly a bug which absolutely requires fixing, but as described in the article, these data were not backed up. And if they had been properly backed up, nothing would have been lost. Unless that 250Gb had just been captured in the previous few hours (unlikely, albeit not impossible), then it should have already been backed up elsewhere long ago. As a previous poster said, the bit about 'federally funded research' is simply a whiny confession that someone wasn't being particularly dilligent.

the bug was about 'move', not copy

Maybe I missed something in the previous comments but it seems nobody noticed that the widely known bug was only about 'move' operation and no report has complained about 'copy', which should be safe.
So my guess is that there was either something wrong with your old disk, or you did not tell the whole story of how you operated.

BTW, if you have not touched your old disk (writing into it etc), try FileSalvage. It might be able to help you recover your files.

Finder bug

I suspect this is the well documented "Finder Data Loss Bug", apparently it was fixed in the Mac OS X 10.5.1 update.

"move, not copy"

I am not an expert but isn't the Finder default behavior to copy when you try to move data to and external device?

Thanks for the heads up!

A seemingly innocent task, gone so wrong! As a scientist, it makes me want to cry when I hear about things like that. I hope you are able to recover at least some of it!

Has anyone with 2 external

Has anyone with 2 external drives attempted to reproduce this bug in 10.5.1? This would be the sort of thing to verify in detail, so that it can be radar reported and fixed. Especially since, if it does exist in 10.5.1, it is supposedly different from the other data loss bug people are talking about from 10.5.0.

Re: Much easier to blame the victim, eh?

First, this is (was?) indeed a bug in MacOS, that I'd rate as critical.

Sorry if I hurt your feelings, I guess it's difficult to criticize (in a constructive way) someone who has just gone through bad things. I understand the feeling, by the way, even though I've not yet lost any important data myself, working in academic research gives you plenty of examples in people around you... because we often have to deal with large volumes of data.

But I still think there is a point, however. It's a bit like in airplanes: backup is about redudancy. If a single fault of a single system, how crude it might be, makes you loose data, then the backup plan isn't working (or, you've decided that any data implied in it is not worth doing more, which doesn't seem to be the case here).

PS: It might not have been clear from my previous comment, but I'm also working in academia, and manipulate precious resources (data or CPU time) funded by the taxpayer.

Not just in Leopard

First post here guys and this thread caught my eye right off. I made this mistake once in Tiger and yes it is a mistake to “move” valuable information instead of copying it. I really don't know if it's a bug or not I have done some research on the subject and the same thing can happen in the Windows world when you move something instead of copying it. I believe “moving” files is fine if it's under a GB but anything over that I would copy.

Moving files over a network or even and external drive is a real bad idea on any OS. Especially if you don't have a backup.

I lost GB's of info thinking I would save myself some time moving the files instead of copying them, I was wrong. I did have a backup but it still took more time to recover the lost info than it would've if I had just copied the files.